Surgical adhesive

ABSTRACT

Elastomeric or flexible surgical adhesives, comprising [A] NCO-terminated hydrophilic urethane prepolymer derived from hydrophilic polyether polyol of higher oxyethylene content, or combination of [A] with [B] unsaturated cyano compound containing cyano group attached to a carbon atom constituting the polymerizable double bond, are used for bonding of tissues, with rapid cure rate and sufficient bonding power.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to surgical adhesive.

2. Description of the Prior Art

It is known that urethane prepolymer from polyester is used as surgicaladhesive (Progr. neurol. Surg., Vol. 3, pp. 116-168, Karger, BaselandYearn Book, Chicago 1969).

Such prepolymer, however, has drawbacks that, due to its very slow andununiform curing characteristics, poor adhesive strength has been oftenfound, as applied in vascular graft, resulting in massive bleeding.

SUMMARY OF THE INVENTION

It is an object of the present invention to provide a rapidly curablesurgical adhesive.

It is another object of this invention to provide an surgical adhesivehaving high improved bonding power for tissues.

It is still another object of the invention to provide surgical bondingmeans with improved elasticity or flexibility.

It is yet another object of the invention to provide adhesive forsurgery of lower toxicity.

Briefly, these and other objects of the present invention as hereinafterwill become more readily apparent have been attained broadly by asurgical adhesive, which comprises [A] NCO-terminated hydrophilicurethane prepolymer derived from hydrophilic polyether polyol of higheroxyethylene content, or combination of [A] with [B] unsaturated cyanocompound containing cyano group attached to a carbon atom constitutingthe polymerizable double bond.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Said NCO-terminated hydrophilic urethane prepolymer [A], used in thesurgical adhesive according to the invention, can be derived from atleast one organic polyisocyanate (a) and at least one hydrophilicpolyether polyol (b) with or without one or more other polyols (c).

Illustrative of suitable hydrophilic polyether polyols (b) are adductsof ethylene oxide [hereinafter referred to as EO] or combinationsthereof with other alkylene oxide(s) [hereinafter refferred to as AO] toone or more compounds containing at least two active hydrogen atoms,such as polyhydric alcohols, polyhydric phenols, amines, polycarboxylicacids, phosphorous acids and the like. Suitable examples of polyhydricalcohols include dihydric alcohols, such as ethylene glycol, propyleneglycol, 1,3- and 1,4-butane diols, 1,6-hexane diol, neopentyl glycol,diethylene glycol, bis(hydroxymethyl)cyclohexane,bis(hydroxyethyl)benzene, hydrogenated bisphenol A, hydrogenatedbisphenol F, polytetramethylene glycols, polyester diols andsilanol-terminated polysiloxanes; trihydric alcohols, such as glycerol,trimethylol propane, trimethylol ethane, 1,2,3-butane triol,1,2,6-hexane triol and polyester triols; and polyhydric alcohols having4-8 or more hydroxyl groups, such as pentaerythritol, diglycerol,alpha-methylglucoside, sorbitol, xylitol, mannitol, glucose, fructose,sucrose, and the like. Exemplary of suitable polyhydric phenols aremono- and poly-nuclear phenols, such as hydroquinone, catechol,resorcin, pyrogallol, and bisphenols [bisphenol A, bisphenol F,bisphenol S and the like], as well as phenol-formaldehyde condensationproducts. Suitable amines are inclusive of ammonia; alkanol amines, suchas mono-, di- and tri-ethanol amines, isopropanol amines and the like;aliphatic, aromatic, araliphatic and alicyclic monoamines, such as C₁-C₂₀ alkyl amines [methyl, ethyl, isopropyl, butyl, octyl and laurylamines, and the like], aniline, toluidine, naphthyl amines, benzylamine, cyclohexyl amine and the like, aliphatic, aromatic, araliphaticand alicyclic polyamines, such as C₂ -C₆ alkylene diamines [ethylenediamines], diethylene triamine, tolylenediamines, phenylenediamines,xylylenediamines, methylenedianilines, diphenyletherdiamines,isophoronediamine, cyclohexylenediamines, dicyclohexylmethanediaminesand the like; and heterocyclic polyamines, such as piperazine,N-aminoethyl-piperazine, and other heterocyclic polyamines, written inJapan Patent Publication No. 21044/1980.

Suitable AO, which may be employed in combination with EO for producingpolyether polyols, include, for example, propylene oxide [hereinafterreferred to as PO], 1,2- 2,3- ,1,3- and 1,4-butylene oxides, styreneoxide, epichlorohydrin and the like, as well as combinations of two ormore of them. Among these, preferred are PO.

Addition of EO or combination thereof with AO to active hydrogenatom-containing compounds can be carried out in the usual way, with orwithout catalysts [such as alkaline catalysts, amine catalysts andacidic catalysts], under normal or an elevated pressure, in a singlestep or multi-stages. Addition of EO and AO may be performed byrandom-addition, block-addition or combination of them [for instancerandom-addition followed by block-addition]. Preferred israndom-addition.

Hydrophilic polyether polyols have equivalent weight (molecular weightper hydroxyl group) of usually 100-5,000, preferably 200-3,000, andoxyethylene content of usually at least 30%, preferably 50-90% byweight. Polyether polyols having equivalent weight higher than 5,000 aretoo viscous to be used as surgical adhesives; while equivalent weightless than 100 results in lack of flexibility required for surgicaladhesives. Polyether polyols of oxyethylene content less than 30% byweight, having insufficient hydrophilic nature, have poor reactivitywith body fluids resulting in reduced cure rate and poor bonding powerwith water-rich tissue. Content of the primary hydroxyl groups ofpolyether polyols is preferably at least 30%, more preferably at least50%, most preferably at least 70%.

Other polyols (c), optionally used in conjunction with hydrophilicpolyether polyols, include low molecular weight polyols and/orhydrophobic polyols. Examples of such polyols are polyhydric alcoholsmentioned above [as raw materials for hydrophilic polyether polyols]; AOadducts (such as PO adducts) of these polyhydric alcohols or otheractive hydrogen atom-containing compounds; and polyester polyols.Illustrative examples of polyester polyols are condensation products ofdihydric and/or trihydric alcohols [ethylene glycol, propylene glycol,1,3- and 1,4-butane diols, 1,6-hexane diol, neopentyl glycol, diethyleneglycol, glycerol, trimethylolpropane and the like] and/or polyetherpolyols [such as those described above] with dicarboxylic acids[aliphatic or aromatic dicarboxylic acids, such as glutaric, adipic,sebacic, fumaric, maleic, phthalic and terephthalic acids] orester-forming derivatives thereof [anhydrides and lower alkyl esters,such as maleic and phthalic anhydrides, dimethyl terephtharate, and thelike]; ring-opening polymerization products of lactones [such asepsilon-caprolactone]. Among these polyols, polyether polyols arepreferred to polyester polyols.

These polyols [(b) and optionally (c)], used for producingNCO-terminated urethane prepolymer, have equivalent weight (average) ofusually 100-5,000, preferably 200-3,000 and usually 2-8 hydroxyl groups,preferably 2-4 hydroxyl groups.

Suitable polyisocyanates, used in producing NCO-terminated hydrophilicurethane prepolymer [A] according to the invention, include, forexample, aromatic polyisocyanates containing 6-20 carbon atoms [exceptcarbon atoms in NCO groups], such as o-, m- and p-phenylenediisocyanates [hereinafter referred to as PDI], 2,4- and2,6-tolylenediisocyanates [TDI], diphenylmethane-2,4'- and4,4'-diisocyanates [MDI], naphthalene-1,5-diisocyanate,triphenylmethane-4,4',4"-triisocyanate,polymethylenepolyphenylenepolyisocyanates [PAPI] obtained byphosgenation of aniline-formaldehyde condensation products, m- andp-isocyanato-phenyl sulfonyl isocyanate, and the like; aliphaticpolyisocyanates containing 2-18 carbon atoms, such asethylenediisocyanate, tetramethylenediisocyanate,hexamethylenediisocyanate, dodecamethylenediisocyanate,1,6,11-undecanediisocyanate, 2,2,4-trimethylhexanediisocyanate, lysinediisocyanate, 2,6-diisocyanato-methyl caproate, bis(2-isocyanato-ethylfumarate, bis(2-iso-cyanato-ethyl)carbonate,2-isocyanato-ethyl-2,6-diiso-cyanato-hexanoate, and the like; alicyclicpolyisocyanates containing 4-15 carbon atoms, such as isophoronediisocyanate, dicyclohexylmethane diisocyan-ates, cyclohexylenediisocyanates, methylcyclohexylene diisocyanates,bis(2-isocyanato-ethyl) 4-cyclohexene-1,2-dicarboxylate, and the like;araliphatic polyisocyanates containing 8-15 carbon atoms, such asxylylene diisocyanates, diethylbenzene diisocyanates, and the like; andmodified polyisocyanates of these polyisocyanates, containing urethane,carbodiimide, allophanate, urea, biuret, urethdione, urethimine,isocyanurate and/or oxazolidone groups, such as urethane-modified TDI,carbodiimide-modified MDI, urethane-modified MDI, and the like; as wellas mixtures of two or more of them.

Among these polyisocyanates, preferred are aromatic polyisocyanates(preferably diisocyanates), particularly PDI, TDI [including 2,4- and2,6-isomers, mixtures of them and crude TDI], MDI [including 4,4'- and2,4'-isomers, mixtures of them and crude MDI or PAPI], and modifiedpolyisocyanates containing urethane, carbodiimide, allophanate, urea,biuret and/or isocyanurate groups, derived from PDI, TDI and/or MDI.

The most preferred is p-PDI [hereinafter referred to as PPDI], withrespect to low toxicity. Combinations of PPDI with a minor amount(usually up to 50% by weight, preferably up to 30% by weight) of one ormore other polyisocyanates, as memtioned above. Among said otherpolyisocyanates, used in conjunction with PPDI, are aromaticpolyisocyanates, particularly TDI and MDI [including crude ones andmodified ones] and mixtures of them. It is preferred to react said otherpolyisocyanates at early stages of prepolymer production so as toprovide PPDI terminated prepolymers.

In reacting at least one polyisocyanate (a) with at least onehydrophilic polyether polyol (b) and optionally one or more otherpolyols (c) to form NCO-terminated hydrophilic urethane prepolymers,ratio of NCO/OH is generally 1.5-5.0, preferably 1.7-3.0. The reactionof (a) with (b) and optionally (c) forming prepolymers can be performedin the usual manner. The reaction may be carried out in the presence ofa catalyst. Prepolymers may be prepared by reacting (a) with a mixtureof (b) and (c), or reacting successively in any order with (b) and (c).Prepolymers may be prepared by blending a prepolymer from (b) with aprepolymer from (c) [for instance, blending with a prepolymer from a lowmolecular weight polyol (equivalent weight 50-500) to reduce viscosity].

NCO-contents of NCO-terminated hydrophilic prepolymers are usually1-10%, preferably 2-8% by weight. Prepolymers of NCO-content less than1% by weight are of poor reactivity and bring about reduction of curerate and insufficient bonding power to tissues. Higher NCO-content than10% by weight results in brittle cured resins of poor flexibility whichare not deformable following the movement of living organism.

Illustrative examples of suitable unsaturated cyano compound [B]containing cyano group attached to a carbon atom constituting thepolymerizable double bond are cyano(meth)acrylic acids [cyanoacrylicacid and cyanomethacrylic acid; similar expressions are usedhereinafter]; cyano(meth)acrylic esters, such as methylcyano(meth)acrylates, ethyl cyano(meth)acrylates, iso-butylcyano(meth)acrylates and the like; (meth)acrylonitriles,cyano(meth)acrylonitriles, and the like; and mixtures of two or more ofthese compounds. Among these, preferred are cyanoacrylic esters,especially methyl cyanoacrylate, ethyl cyanoacrylate and iso-butylcyanoacrylate.

In adhesive compositions comprising said hydrophilic urethane prepolymer[A] and said unsaturated cyano compound [B], content of [A] is usually20-90%, preferably 30-70%, based on the total weight of [A] and [B]. Useof less than 20% of [A] results in poor flexibility and poor bondingability with living organism. Combination of [A] with 10% or more of [B]provide more rapid cure rate, which can be applied for bonding of bloodvessels, wherein quick-curing is required. By varying the ratio of [A]to [B], there can be attained desired hardness in accordance withmovement of living organism. Adhesives containing higher amount of [A]are effective for applications requiring flexibility, such as bonding ofblood vessels; while adhesives of lower content of [A], providingrelatively higher rigidity, are suitable for bonding of bone orcircumference thereof.

Adhesives of this invention may contain, if necessary, fillers [forexample, carbon black, metal oxides, such as red iron oxide and titaniumdioxide, silicates, such as calcium silicates and sodium silicates,acrylic resin powders, various ceramic powders, and the like]; softeningagents [such as DBP(dibutylphosphate), DOP(dioctylphosphate),TCP(tricresylphosphate), tributoxyethylphosphates, and other esters ofvarious types]; stabilizers, such as trimethyldihydroquinone,phenyl-betanaphthyl amine, p-isopropoxydiphenylamine,diphenyl-p-phenylene diamine, and the like. These additives may be usedin an amounts of usually 0-20%, preferably 0-5%, based on the weight ofthe adhesive according to the invention.

Both said NCO-terminated prepolymer(s) and said cyano compound(s) canbring about rapid polymerization in the presence of trace amounts ofwater such as moisture in air and result in forming tough membrane.Accordingly, it is necessary to use dehydrated ones as these maincomponents and also other compounding additives, and it is preferred toshut off air during production of adhesives. Adhesives, thus obtained,can be stored for a long period of time within airtight vessels, such asampule.

In applying adhesives of the present invention in surgery, applicationmethods include those by using brushes, tweezers, applicators,specially-designed spatula or syringes, or the like; and those by spraycoating using innert gases, such as Freons, nitrogen or the like.Bonding of tissues can be achieved, for example, by direct coatingtechniques, simply applying the adhesive to the tissues; bycover-coating techniques, using, as an aid for hemostasis oranastomosis, thin sheets or meshes made of polyesters (such as Dacron),oxidized celllose, collagen, polyurethanes or the like, cotton-likematerials, or fragments or tissues, such as veins, musculation ormascular membrane or the like [wherein these materials are applied ontothe affected parts followed by coating thereon the adhesives]; or bysealing techniques for sutured parts, wherein sutures are partly appliedfollowed by applying the adhesive to seal the remaining conjugationparts. The adhesives of the invention can be used, not only for tissueadhesion, but also as coating, embolus or sealing materials incardiovascular surgery via direct coating or injection by catheters.Applicable tissues include, for example, blood vessels, heart, lung,esophagus, stomach, skin and the like.

Having generally described the invention, a more complete understandingcan be obtained by reference to certain specific examples, which areincluded for purposes of illustration only and are not intended to belimiting unless otherwise specified.

Raw materials used in the following examples are as follows:

PEO: Polyethyleneoxide,

PPO: Polypropyleneoxide,

PEG: polyetheleneglycol,

PPG: Polypropyleneglycol,

PTMG: Polytetramethyleneglycol,

ECA: Ethyl cyanoacrylate,

MCA: Methyl cyanoacrylate,

BCA: Iso-butyl cyanoacrylate.

[Preparation of Prepolymers]

NCO-terminated prepolymers A1 to A4, B1 to B4 and I to III were preparedby mixing each polyether polyol, dehydrated under reduced pressure, witheach polyisocyanate and reacting them for 8 hours at 80 C.

Prepolymer A1

A polyether polyol [a PEO/PPO random copolymer having an average M.W. of3,000 and oxyethylene content of 80%] was reacted with PPDI to obtain aNCO-terminated hydrophilic urethane prepolymer having an NCO-content of2.5%.

Prepolymer A2

A polyether polyol [a PEO/PPO random copolymer having an average M.W. of4,000 and oxyethylene content of 60%] was reacted with PPDI to obtain aNCO-terminated hydrophilic urethane prepolymer having an NCO-content of3.5%.

Prepolymer A3

A polyether polyol [a mixture of 80 parts of a PEG having an averageM.W. of 2,000 and 20 parts of polypropyleneglycol having an average M.W.of 200] was reacted with PPDI to obtain a NCO-terminated hydrophilicurethane prepolymer having an NCO-content of 6.4%.

Prepolymer A4

A polyether polyol [a PTMG-PEO block copolymer having an average M.W. of2,000 and oxyethylene content of 50%] was reacted with PPDI to obtain aNCO-terminated hydrophilic urethane prepolymer having an NCO-content of6.7%.

Prepolymer B1

A polyether polyol [a PEO/PPO random copolymer having an average M.W. of3,000 and oxyethylene content of 80%] was reacted with TDI to obtain aNCO-terminated hydrophilic urethane prepolymer having an NCO-content of2.5%.

Prepolymer B2

A polyether polyol [a PEO/PPO random copolymer having an average M.W. of4,000 and oxyethylene content of 60%] was reacted with MDI to obtain aNCO-terminated hydrophilic urethane prepolymer having an NCO-content of3.5%.

Prepolymer B3

A polyether polyol [a mixture of 80 parts of a PEG having an averageM.W. of 2,000 and 20 parts of polypropyleneglycol having an average M.W.of 200] was reacted with TDI to obtain a NCO-terminated hydrophilicurethane prepolymer having an NCO-content of 6.4%.

Prepolymer B4

A polyether polyol [a PTMG-PEO block copolymer having an average M.W. of2,000 and oxyethylene content of 50%] was reacted with TDI to obtain aNCO-terminated hydrophilic urethane prepolymer having an NCO-content of6.7%.

Prepolymer I

A polyether polyol [a PTMG having an average M.W. of 1,000] was reactedTDI to obtain a NCO-terminated hydrophobic urethane prepolymer having anNCO-content of 6.7%.

Prepolymer II

A polyether polyol [a PEO/PPO random copolymer having an average M.W. of3,000 and oxyethylene content of 20%] was reacted with TDI to obtain aNCO-terminated hydrophobic urethane prepolymer having an NCO-content of2.5%.

Prepolymer III

A polyether polyol [a PEO/PPO random copolymer having an average M.W. of3,000 and oxyethylene content of 10%] was reacted with TDI to obtain aNCO-terminated hydrophobic urethane prepolymer having an NCO-content of2.5%.

[Preparation of Surgical Adhesives]

Surgical adhesives as follows were prepared.

EXAMPLES 1 TO 4

Surgical adhesives consisting essentially of Prepolymers A1, A2, A3 andA4, respectively.

EXAMPLE 5

A surgical adhesive, obtained by mixing and dehydrating 50 parts ofPrepolymer A1 with 50 parts of ECA.

EXAMPLES 6 TO 10

Surgical adhesives, obtained by substituting Prepolymers B1, B2, B3 andB4 for Prepolymers A1, A2, A3 and A4, respectively.

EXAMPLE 11

A surgical adhesive, obtained by mixing and dehydrating 70 parts ofPrepolymer B2 with 30 parts of MCA.

EXAMPLE 12

A surgical adhesive, obtained by mixing and dehydrating 50 parts ofPrepolymer B3 with 50 parts of BCA.

EXAMPLE 13

A surgical adhesive, obtained by mixing and dehydrating 40 parts ofPrepolymer B4 with 60 parts of ECA.

COMPARATIVE EXAMPLE 1

A surgical adhesive consisting essentially of ECA.

COMPARATIVE EXAMPLES 2 AND 3

Surgical adhesive consisting essentially of Prepolymers I and II,respectively.

COMPARATIVE EXAMPLE 4

A surgical adhesive, obtained by dissolving 7 parts of a nitrile rubber(nitrile content: 38-40%) into 50 parts of dehydrated dry nitromethane,followed by adding thereto under stirring 7 parts of ECA and 1 part ofTDI.

COMPARATIVE EXAMPLE 5

A surgical adhesive, obtained by mixing and dehydrating 50 parts ofPrepolymer III with 50 parts of ECA.

[Testing of Surgical Adhesives]

Carotid artery of goat, heparinized in order to avoid effects of bloodcoagulation, was clamped at about 5 cm of distance and then incised 3 mmalong with the longitudinal direction, followed by coating a smallamount of each adhesive. Within several minutes after application of theadhesive, the clamps were removed. Then, the tissue adhesivity andhemostasis were carefully evaluated.

The results were as shown in Table 1.

                                      TABLE 1                                     __________________________________________________________________________    Surgical                                                                      Adhesive                                                                             Cure Time (sec.)                                                                       Flexibility                                                                         Bonding Power                                                                         Clinical sign at adhesive                       __________________________________________________________________________                                  joints                                          Example                                                                       1      25       ○                                                                            ○                                                                              Very good adhesivity. No bleeding                                             after declamping.                               2      24       ○                                                                            ○                                                                              Very good adhesivity. No bleeding                                             after declamping.                               3      20       ○                                                                            ○                                                                              Very good adhesivity. No bleeding                                             after declamping.                               4      35       ○                                                                            ○                                                                              Very good adhesivity. No bleeding                                             after declamping.                               5       7       ○                                                                            ○                                                                              Very good adhesivity. No bleeding                                             after declamping.                               6      35       ○                                                                            ○                                                                              Very good adhesivity. No bleeding                                             after declamping.                               7      36       ○                                                                            ○                                                                              Very good adhesivity. No bleeding                                             after declamping.                               8      29       ○                                                                            ○                                                                              Very good adhesivity. No bleeding                                             after declamping.                               9      42       ○                                                                            ○                                                                              Very good adhesivity. No bleeding                                             after declamping.                               10     10       ○                                                                            ○                                                                              Very good adhesivity. No bleeding                                             after declamping.                               11     15       ○                                                                            ○                                                                              Very good adhesivity. No bleeding                                             after declamping.                               12      9       ○                                                                            ○                                                                              Very good adhesivity. No bleeding                                             after declamping.                               13     10       ○                                                                            ○                                                                              Very good adhesivity. No bleeding                                             after declamping.                               Comparative                                                                   Example                                                                       1       5       ×                                                                             × Very fast curing. Delamination immediately                                    after                                                                         declamping. Massive bleeding.                   2      ≧ 400                                                                           ○                                                                            × Slow and inhomogeneous curing                                                 characteristics.                                                              Bleeding from adhesive joints                   3      400      ○                                                                            × Very slow curing. Due to premature curing,                                    bleeding after declamping.                      4      350      ○                                                                            Δ Very slow curing. Premature curing.                                           Bleeding.                                       5      400      ○                                                                            × Very slow curing. Inhomogeneous curing.                                       Bleeding from adhesive joints                   __________________________________________________________________________

What is claimed as new and desired to be secured by Letters Patentis:
 1. A surgical adhesive, which comprises:(A) at least oneNCO-terminated hydrophilic urethane prepolymer, derived from at leastone organic polyisocyanate and a polyol component comprising at leastone hydrophilic polyether polyol having an oxyethylene content of atleast 30%; and (B) at least one unsaturated cyano compound containing acyano group attached to a carbon atom constituting the polymerizabledouble bond.
 2. The adhesive of claim 1, wherein said prepolymer has anisocyanate-content of 1-10% by weight.
 3. The adhesive of claim 1,wherein said polyol component has an oxyethylene content of at least30%.
 4. The adhesive of claim 1, wherein said polyol component has anequivalent weight (average) of 100-5,000 and a functionality (average)of 2-8.
 5. The adhesive of claim 1, wherein said polyisocyanate is atleast one selected from the group consisting of aromatic polyisocyanatescontaining 6-20 carbon atoms, aliphatic polyisocyanates containing 2-18carbon atoms, alicyclic polyisocyanates containing 4-15 carbon atoms,araliphatic polyisocyanates containing 8-15 carbon atoms, except carbonatoms in NCO groups, and modified polyisocyanates of thesepolyisocyanates containing one or more of urethane, carbodiimide,allophanate, urea, biuret, urethdione, urethimine, isocyanurate andoxazolidone groups.
 6. The adhesive of claim 1, wherein saidpolyisocyanate is p-phenylene diisocyanate, or a combination thereofwith one or more other polyisocyanates.
 7. The adhesive of claim 1,wherein said hydrophilic polyether polyol is at least one adduct ofethylene oxide or a combination thereof with one or more other alkyleneoxides to at least one compound containing two or more active hydrogenatoms.
 8. The adhesive of claim 7, wherein said compound containing twoor more active hydrogen atoms is at least one selected from the groupconsisting of polyhydric alcohols, polyhydric phenols, amines,polycarboxylic acids and phosphorous acids.
 9. The adhesive of claim 1,wherein said hydrophilic polyether polyol is at least one selected fromthe group consisting of polyoxyethylene polyols,polyoxyethylene/oxypropylene polyols and polyoxyethylene/oxybutylenepolyols.
 10. The adhesive of claim 1, wherein said said polyol componentcomprises said hydrophilic polyether polyol and at least one otherpolyol selected from the group consisting of low molecular weightpolyols, hydrophobic polyether polyols and polyester polyols.
 11. Theadhesive of claim 1, wherein said prepolymer is obtained by reactingsaid polyisocyanate with said polyol component in such an amountproviding NCO/OH ratio of 1.5-5.0.
 12. The adhesive of claim 1, whichcomprises 20-90% by weight of said prepolymer and 10-80% by weight ofsaid cyano compound.
 13. The adhesive of claim 1, wherein said cyanocompound is at least one compound selected from the group consisting ofcyanoacrylic acid, cyanomethacrylic acid, cyanoacrylates,cyanomethacrylates, acrylonitrile, methacrylonitrile, cyanoacrylonitrileand cyanomethacrylonitrile.
 14. The adhesive of claim 1, wherein saidcyano compound is at least one cyanoacrylic ester selected from thegroup consisting of methyl cyanoacrylate, ethyl cyanoacrylate ndiso-butyl cyanoacrylate.
 15. The adhesive of claim 1, which contains upto 20% by weight of at least one additive selected from the groupconsisting of carbon black, metal oxides, silicates, acrylic resinpowders, ceramic powders, softening agents, and stabilizers.